By applying a nitride semiconductor, for example, semiconductor light emitting devices such as light emitting diodes (LEDs) of UV, blue and green and laser diodes (LDs) of blue-violet, blue and green have been developed.
In order to enhance the efficiency of semiconductor light emitting devices, it is important to enhance the crystallinity of the semiconductor layer, to reduce nonradiative recombination centers, and to enhance the internal quantum efficiency. Moreover, the activation rate of p-type impurities in the semiconductor layer is low. Consequently, the density of holes tends to be low. Therefore, the improvement of the injection efficiency of holes is required. Moreover, the reduction of operating voltage is required in semiconductor light emitting devices.